A new method for the maintenance of fetal liver in organ culture has been developed. The method is suitable for the study of fetal liver from multiple species and from fetuses of a wide range of gestational ages. The fetal tissues can be maintained for prolonged periods in vitro. Histologic evidence of tissue integrity has been established. Measurements of metabolic function show good reproducibility. Specific measurements of parenchymal cell function show that these remain intact. Initial studies of bile acid metabolism by these tissues are being performed. Cholesterol synthesis, bile acid synthesis, and bile acid conjugation are being examined using this technique. Studies in several other areas of liver function are also projected. Studies of the interaction of viral agents and hepatotoxins with fetal hepatic tissue are in progress, and are projected to continue during the coming year.